Process for undercoating a support of photographic material

ABSTRACT

A process for undercoating a support of a photographic material is disclosed comprising providing an undercoat layer containing gelatin and a basic substance, such as sodium hydroxide, on an activated surface of a support comprising a polyolefin film or a polyolefin-coated film, said basic substance being included therein so as to maintain the hydrogen ion concentration (pH) of the surface of the undercoat layer at a level of from 6.6 to 9.5. A photographic emulsion adheres firmly to the undercoated surface of the support with a markedly increased bond strength.

ttes l 1 inagavva [30] Foreign Application Priority Data Sept. 24, 1970 Japan 45-83649 [52] US. Cl. 96/87 R, 96/85, 117/34,

, 117/47 A [51] Int. Cl G03c 1/80, G03c H86 [58] Field of Search 96/85, 87 R; 117/47 A, 34

[56] References Cited UNITED STATES PATENTS 3,320,191 5/1967 Secrist 96/87 R [4 Jan. 22, 1974 3,161,519 12/1964 Alsup 96/85 3,123,492 3/1964 Maffet 96/87 R FOREIGN PATENTS OR APPLICATIONS 1,134,211 11/1964 Great Britain 96/85 Primary ExaminerRonald H. Smith Attorney, Agent, or Firm-Richard C. Sughrue et a1.

[ 5 7 ABSTRACT A process for undercoating a support of a photographic material is disclosed comprising providing an undercoat layer containing gelatin and a basic substance, such as sodium hydroxide, on an activated surface of a support comprising a polyolefin film or a polyolefin-coated film, said basic substance being included therein so as to maintain the hydrogen ion concentration (pl-l) of the surface of theundercoat layer at a level of from 6.6 to 9.5. A photographic emulsion adheres firmly to the undercoated surface of the sup-' port with a markedly increased bond strength.

7 Claims, No Drawings PROCESS FOR UNDERCOATING A SUPPORT OF PHOTOGRAPHIC MATERIAL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for undercoating a photographic material support composed of a polyolefin film or a polyolefin-coated film.

2. Description of the Prior Art A polyolefin surface is chemically inert, and therefore, when a photographic emulsion is directly coated on such a surface, the support does not adhere at all to the photographic emulsion layer. Accordingly, it has previously been the practice to subject such a polyolefin surface to an activating treatment such as a coronadischarge treatment, or a flame treatment, before applying a photographic emulsion layer to the surface.

Furthermore, in order to prevent the deterioration of the activating treatment effect with the passage of time before the application of a photographic emulsion, un-

dercoating of the activated polyolefin surface with a hydrophilic resin has previously been performed.

However, neither the activating treatment nor the undercoating after the activating treatment has given a practically satisfactory bond strength between the support and the photographic emulsion layer.

Extensive work on undercoating methods in an attempt to remove these defects of the prior art has finally led to the accomplishment of the present invention.

SUMMARY OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS:

The support used in this invention is a polyolefin film or a polyolefin-coated film obtained by coating at least one surface of a support made of a material such as paper, cellophane, cellulose acetate or polyester, with a polyolefin. By the term polyolefin, as used in the present specification, is meant polyethylene, polypropylene or mixtures thereof. The polyolefin film is obtained by an ordinary film-forming method such as the tubular film method, or flat die method. The polyolefin-coated film is obtained by the extrusion coating method or the adhering method using an adhesive.

The undercoat layer in the present invention consists essentially of gelatin. The undercoat layer is prepared by coating an aqueous solution of gelatin or a dispersion of an aqueous gelatin solution in an organic solvent compatible with water, onto the surface of a polyolefin support which has been subjected to the activating treatment. The gelatin solution preferably has a concentration of from 0.1 to 15 percent by weight.

Suitable activating treatments, known to those skilled in the art, can be employed depending on the characteristics desired. An example of a suitable activating treatment is disclosed in Tappi, Volume 48, No. 9; September, 1965; pps. -84.

The pH adjustment of the surface of the undercoat layer is effected by adding any water-soluble hydrophilic basic substance to the under-coat solution. Examples of typical basic substances include sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate, although it is to be expressly understood that any hydrophilic basic substance which performs the function of adjusting the pH to from 6.6 to 9.5, is operable.

The polyolefin film or coating of the support preferably has a thickness of from about 10 to microns and the undercoat layer preferably has a thickness of from about 0.01 to 10 microns.

In addition, if desired, the undercoat layer can have incorporated therein up to about 30 percent by weight of a low molecular weight carboxylic acid, such as, for example, formic acid, propionic acid, acrylic acid or salicylic acid. The acid is added to the layer in order to stabilize the colloidal gelatin in the non-soluble liquid medium.

The measurement of the pH of the undercoat surface was made by a color test using a litmus solution and a color test using a paper surface pH measuring solution (product of Kabushiki Kaisha Kyoritsu Rikagaku Ken kyusho).

The bond strength between the support and the photographic emulsion layer was measured as follows:

1. Bond strength in -a dry state after or before the photographic processing:

Checkerboard like, criss-crossing lines (the space between the lines being about 4 mm) were provided on the emulsion surface of the support using a razor blade. An adhesive tape was applied to it from above, and then peeled off quickly. When more than 90 percent of the emulsion surface remained unpeeled, the bond strength was evaluated as good.

2. Bond strength in a processing solution:

One scratch, i.e., score, was made on the emulsion surface while the material was immersed in a processing solution using a stylus, and the injured, i.e., scored, portion was rubbed with a finger tip at right angles to the injury. When the photographic emulsion layer did not come off more than the injury, the bond strength was evaluated as good.

In tests with the photographic material using the support and undercoat layer of the present invention, the bond strength between the support and the photographic emulsion layer was always evaluated as good.

The invention will now be described specifically by the following Examples which are presented for illustrative, rather than limitative purposes.

EXAMPLE I Polyethylene having a density of 0.92 g/cm was extrusion-coated onto both surfaces of a photographic raw paper having a unit weight of g/m in a thickness of about 30 microns. One surface of the polyethylene-coated paper onto which a photographic emulsion was to be coated was subjected to a corona discharge treatment using a corona discharge apparatus having a movable electrode and disposed at a position 0.8 mm away from said surface. The discharge output per unit length of the electrode was 10 W/cm, and the electrode 3 4 moving speed of 20 m/min. Thereafter, each under- Formulation 41 coating solution of the following formulations, Nos. 1 Gelatin 5 g and 2, was coated on to separate samples, each having salicylic acid g I the treated surface as described above, and dried. Sodium carbonate 1 5 Water 300 cc Formulation No. 1 Methanol 700 cc Gelatin 50 g A gelatin-silver halide emulsion was coated onto Water 400 cc each samples undercoated surface of the polypropyl- M h 600 cc ene film, and the bond strength between the support 10 and the photographic emulsion layer was measured, Formulation No. 2. and the results are shown in Table 2.

Table 2 Bond strength Formulation pH values of Dry state (per- Wet state of the underthe undercentage of (maximum width of coating coated unpeeled emulthe peeled emulsolution surface sion layer) sion layer) No. 3 5.2 70 75% mm No. 4 6.8 90 100% 0 mm Gelatin 50 g EXAMPLE 3 Sodlum hydroxlde g Different portions of one surface of a high density Water 400 cc polyethylene film having a thickness of 150 microns, Methanol 600 cc The undercoated surfaces of each polyethylenecoated paper were coated with an ordinary photographic emulsion.

The bond strength between the support and the emulsion layer of each of the resultant water-resistant photographic papers was measured, and the results are shown in Table l. The pH values of the undercoated surfaces of the polyethylene-coated papers are also shown in Table 1.

Table 1 onto which a photographic emulsion was to be coated, were subjected to a corona discharge treatment using a corona discharge apparatus of the type shown in Example l, and then immediately coated with separate undercoating solutions of the formulations Nos. 5 and Formulation No. 5

Gelatin 75 g Salicylic acid 7.5 g

Bond Strength Formulation pH values of Dry state (per- Wet state of the underthe undercentage of (maximum width coating coated unpeeled emulsion of the peeled solution surface layer) emulsion layer) No. 1 6.2 75-85% 2 3 mm No. 2 6.6 95-100% 0 mm EXAMPLE 2 Water 300 cc Different portions of one surface of a crystalline Methanol 700 cc polypropylene film having a thickness of 150 microns F l ti n N0, 6; were flame treated with a gaseous mixture of propane G l 75 and oxygen, and then immediately coated with separate d g 7 5 undercoating solutions, each of the following formulag g g fiy g tions, Nos. 3 and followed by drying. water 300 cc Methanol 700 cc F Ormulmon NO 3 A gelatin-silver halide emulsion was coated onto W") g each samples undercoated surface of the polyethylene sallcyllc acld 5 g film. The bond strength between the support and the Water 300 cc emulsion layer of the resultant photographic materials Methanol 700 cc was measured. and the results are shown in Table 3.

What is claimed is: i l. A photographic material comprising a support selected from the group consisting of a polyolefin support and a polyolefin-coated support, the surface of said support being activated, having coated thereon an undercoat layer consisting essentially of gelatin and a hydrophilic basic substance present in an amount sufficient to provide the surface of the undercoat layer with a pH of from 6.6 to.9.5 and a photographic emulsion coated onto said undercoat layer.

2. The photographic material of claim 1 wherein the polyolefin is polyethylene, polypropylene or a mixture Table 3 Bond strength Formulation pH values of Dry state Wet state of the underthe under- (percentage of (maximum width coating coated unpeeled emulof the peeled solution surface sion layer) emulsion layer) No.5 5.2 70 75% i5 20 mm No.6 9.5 95 100% 0 mm 5. The photographic material of claim 1, wherein the thickness of said undercoat layer is from about 0.01 to 10 microns.

6. The photographic material of claim 1 wherein the polyolefin portion of said support is from 10 to 100 microns in thickness.

7. A process for producing a photographic material comprising providing an undercoat layer consisting essentially of gelatin and a hydrophilic basic substance on an activated surface of a support selected from the group consisting of a polyolefin support and a polyolefin-coated support, said hydrophilic basic substance being included to maintain the pH of the surface of the undercoat layer at a level of from 6.6 to 9.5, and coating a photographic light-sensitive emulsion onto said undercoat layer. 

2. The photographic material of claim 1 wherein the polyolefin is polyethylene, polypropylene or a mixture thereof.
 3. The photographic material of claim 2, wherein the basic substance is sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate.
 4. The photographic material of claim 2 wherein said undercoat layer further comprises up to about 30 weight percent of a low molecular weight carboxylic acid.
 5. The photographic material of claim 1, wherein the thickness of said undercoat layer is from about 0.01 to 10 microns.
 6. The photographic material of claim 1 wherein the polyolefin portion of said support is from 10 to 100 microns in thickness.
 7. A process for producing a photographic material comprising providing an undercoat layer consisting essentially of gelatin and a hydrophilic basic substance on an activated surface of a support selected from the group consisting of a polyolefin support and a polyolefin-coated support, said hydrophilic basic substance being included to maintain the pH of the surface of the undercoat layer at a level of from 6.6 to 9.5, and coating a photographic light-sensitive emulsion onto said undercoat layer. 